Tuesday, November 6, 2007 - 2:50 PM
149-11
Long-Term Agronomic Performance of Organic and Conventional Field Crops in the Mid-Atlantic Region.
Despite increasing interest in organic grain crop production among farmers, government agencies and other stakeholders, there is little information on expected crop yields and production challenges in organic grain production, especially in Coastal Plain soils of the mid-Atlantic region. The USDA-ARS Beltsville Farming Systems Project (FSP), a long-term cropping systems trial, was established in Maryland in 1996 to address these needs. The five FSP cropping systems include a three-year conventional no-till corn (C)-soybean (S)-wheat (W)/S rotation (NT), a conventional chisel-till C-S-W/S rotation (CT), a two-year organic C-S rotation (Org2), a three-year organic C-S-W rotation (Org3), and a four-to-six year organic C-S-W-hay rotation (Org4+). Average corn grain yield in Org2, Org3, and Org4+ after ten years was less than that in CT (8.03 Mg ha-1) by 41, 31, and 24%, respectively. Low N availability explained 70 to 75%, weed competition explained 21 to 25%, and plant population explained 3 to 5% of lower corn yields in the organic systems than in CT. The positive relationship between corn yield and crop rotation length and complexity among organic systems was related to both greater N availability and lower weed competition in longer rotations, especially when hay was included in the rotation. Soybean yield averaged 19% lower in the three organic systems (2.88 Mg ha-1) than in the conventional systems (3.57 Mg ha-1). Weed competition alone accounted for this difference . There were no consistent differences in wheat yield among systems and crop rotation length had little impact on soybean and wheat yields among organic systems. Results indicate that supplying adequate N for corn and controlling weeds in corn and soybean are the biggest challenges in producing crop yields in organic systems that are equal to those in conventional systems in the mid-Atlantic region, and that increasing crop rotation length can help address both these issues.
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